A common water dispenser includes a body, a base, a heating system, a refrigeration system located in the body, a water drain valve and a water outlet. On the lower part of the base, there is a reservoir or reservoir connecting to the corresponding refrigeration system and heating system through a cold water pipe and a hot water pipe. The outlets of the refrigeration system and heating system are connected to the relevant cold or hot water dispensing valve and water outlet. Thus, when in use, a user only needs to push the corresponding water dispensing valve and then the desired hot, cold or common-temperature is dispensed. In this way, the water dispenser is very convenient. However, the heating system of the aforesaid water dispenser usually uses a conventional tube whose insulating property is not good under the limitation of current structure and material. Therefore, when the water dispenser is on, the temperature of boiled water will decrease with time if water is not timely drunk. Consequently when the temperature of the boiled water in the dispenser decreases to a certain degree (for example 80° C.), the dispenser will reheat the boiled water.
This successive reheating and cooling of the same water has the following drawbacks: 1) It causes a great loss of nutrient contents such as mineral substance and an increase of nitrite ions and thus is unhealthy. 2) The deposit and fouling of the mineralizer generated by mineral substance on the surface of the heating pipe reduces the heating efficiency of the heating pipe and wastes electrical energy. At the same time, the inner tube must be cleared frequently. 3) Long periods of consistent operation will reduce the lifetime of the electric heating tube. In order to deal with these drawbacks, the power of the water dispenser is cut when not used and powered when needed. But in so doing, a user has to wait for a relatively long time to heat the water to a desired temperature. Obviously, this kind of water dispenser is not convenient.
To overcome the above-mentioned drawbacks, a kind of water dispenser has been developed to provide boiled water instantly. For example, Chinese Patent Number 99223771.8 discloses such a water dispenser. It includes a main body, a water tank in the upper part of the main body and a rapid heater in the lower part of the main body. The heater is composed of a UHT electric heating tube and several spiral baffle boards assembled into a heating tank whose water inlet is interlinked with the outlet of the water tank while its water outlet is connected with the hot water funnel through a guide pipe. Though this type of device can timely provide instant boiled water, it cannot be used with delicate multi-purpose household water dispensers due to its large size, complicated structure and additional insulation layer.